Structural panel and method of making the same



Oct. 15, 1957 MacMlLLAN CLEMENTS 2,309,403

STRUCTURAL PANEL ANDMETHOD OF MAKING THE SAME Filed March 51, 1955 1,9INVENTOR.

Mae M71102 C/eme 2,809,403 Fatented Oct. 15, 1957 STRUCTURAL PANEL ANDMETHOD OF MAKING THE SAME MacMillan Clements, Ridgefield, Conn.

Application March 31, 1955, Serial N 0. 498,281

2 Claims. (Cl. -91) This invention relates to structural panels, andmore particularly to the structure of a door composed of such panels.

An object of the invention is to improve the structural characteristicsof a panel, particularly the core thereof, in order to obtain maximumstrength when using a core composed of comparatively thin single orlaminated sheets.

Another object of the invention is to provide an improved method ofmaking a door of the type set forth in the next preceding paragraphabove.

Other objects will appear hereinafter throughout the specification.

In the drawings:

Figure 1 is a partly broken away perspective view of one embodiment ofthe invention;

Figure 2 is a perspective view of certain of the parts shown in Figure 1and with the stiles separated from the core;

Figure 3 is a perspective view of the door showing a typical manner forcompressing the core;

Figure 4 is a broken away view of the core and a vertical sectional viewof the rollers shown in Figure 3;

Figure 5 is a broken away view with the covers about to be applied tosaid core, the covers being shown in vertical section;

Figure 6 is a top plan view of one form of core in place on the bottomcover;

Figure 7 is an enlarged view of a single cell of the core of Figure 6,showing grid cuts therein and the cutters for making said grid cuts; and

Figure 8 is a second form of grid, partly broken away, showing grid cutstherein, and the cutters for making said grid cuts.

Following the successful production and use of the so-called honeycombgrid type of door wherein the grid or core has been compressed duringone of the manufacturing steps thereof to thereby impart better bondingbetween core and cover sheets, as disclosed in my prior Patent No.2,511,620, granted June 13, 1950, various attempts have been made toobtain the improved results of said patented door, but at a reducedcost, see Interior Flush Doors with Standard Honeycomb Cores, ServiceBulletin H-3, published by Union Bag and Paper Corporation, HoneycombDivision, October 6, 1954.

The grid or core of such doors is composed of a plurality of singlestrips of paper, as distinguished from a grid composed of strips eachcomposed of a central corrugated paper member provided with covermembers of paper as shown in Figure 3 of the aforementioned patent.

When a grid composed of a plurality of single strips of paper, as setforth in said Union Bag and Paper Corporation publication, is subjectedto a crushing or pressure treatment as therein described in order tobring it to size and shape it to fit proper thickness of stiles andrails, its internal, i. e., the honeycomb structure, is greatlyweakened. In other words, in order to accomplish the results which havebeen definitely established in the construction shown in theaforementioned patent, wherein a section of corrugated material is usedbetween sheets of paper to form a grid, allowing for compression withoutdistortion or injury to the structural entity of the core, substitutematerials of lesser order are being offered to the trade, as set forthin the aforementioned publication, and it has been found that when usingsaid substitute materials, the door composed in part of said materialsloses a major part of its structural characteristics.

The corrugated box-board core material of said patent, when subjected tocompression, has a tendency to splay outwardly, thereby establishingeven more firmly a true bond between its upper and lower side edges andthe surfaces of the inner and outer sheets to which they are attached.However, grids composed of sheets of very thin material, as taught insaid publication, and wherein the grid composed of said sheets iscrushed, it has been found that the crushing operation causes the sheetsto bend or become S-shaped in cross section, thereby destroying themajor structural characteristics of the socalled honeycomb type of core,and weakening the bond between said core and the cover sheets which arefastened thereto.

The present invention is directed to the use of very thin sheets ofsingle or multiple material and to the method and article which includesthe pre-slicing or cutting of the extra thickness of the core so that aseries of small foldable flanges are formed by a pressing or rollingmeans. These flanges increase the surfaces which are bonded to the coversheets and the said flanges make it possible to provide substantiallystraight connecting sweeps between the cover sheets which sweeps formthe major part of the grid.

In the drawings, the numeral 16 indicates the rectangular frame which iscomposed of the rails or side pieces 12 and the stiles or end pieces 14.Connected to the frame by any suitable means are the front cover 16 andthe back cover 18, as shown in Figure 1. The frame is provided with theusual solid wood block 29 for receiving a lock that is glued orotherwise fastened to the inside of one of the rails. The opposite railis provided with blocks 22,

The grid as a whole is indicated by the reference numeral 24. This iscomposed of a plurality of crossed or interlocked sheets ofcomparatively thin paper, which latter may be composed of single sheetsor of laminated sheets 26. The grid sheets cross each other to formdiamond shaped openings and may be suitably notched for this purpose, asshown for instance in Figure 3 of my patent mentioned above. The sheetsare compressed by the blocks as and 22 when they are placed within theframe 10. The parts of the frame 12 and 14 and the sheets 16 and 18 maybe attached to each other by any suitable means such as nails, glue, orboth, not shown.

Prior to the insertion of the core 24 within the framework, the sheetsare subjected to a series of cutters indicated by reference numeral 28in Figure 8, which cutters, when they pass over the grid, cut a seriesof slots 30, as shown in Figure 8.

The distance of the cut is the same or substantially the same as thedistance that the core projects beyond the frame on opposite sidesthereof. in other words, the core may project one-sixteenth orone-thirty second of an inch on opposite sides of theframe, and thedepth of the cut on the opposite sides of the core in the case of aprojection of one-sixteenth of an inch will be onethirty second of aninch on opposite sides thereof.

Following the cutting operation, which has been diagrammaticallyillustrated in Figure 3, the grid is assembled within the frawework itand both sides thereof are subjected to a compression action by passingthe frame with the grid therein between the rollers 32, as diagramtheupper flange and the bottom surface of the lower flange, as viewed inFigure 4.

Cover sheets 16 and 18 are then applied to opposite sides of theframework, and the core, which is under slight compression, presses theflanges 34 against the inner surfaces of the cover sheets 16 and 18 tothereby cause the same to adhere to said inner surfaces thereof. It willbe noted by reference to Figures 4 and 5 that the sheets 26 aresubstantially straight, because they have not been buckled or formedinto S- or C-shape by the compressing operation. This is due to the factthat the core has been slit at'nurnerous points to form the slots 30,and that the rollers merely bend over the flanges 34 and only apply aninfinitesimal amount of pressure to the vertical portionsof the grid.

Referring to Figures 6 and 7, a truly honeycomb, type of grid has beenshown therein. This grid is formed of a plurality of cells 36 and thesides of the cells are formed with slots 38 by the cutters 44) which arecaused to pass over the honeycomb grid so as to form the slots on boththe upper and lower edges thereof.

One manner of forming slots in both the upper and lower portions of anyof the grids shown in the figures, is to first pass a gang of cutters,such as shown at 28 or 4 as would occur to one skilled in the art towhich the invention relates.

I claim: 7

1. A method of making a structural panel comprising the steps ofproviding a flat cellular core having the cells thereof polygonal incross section and defined by peripherally extending walls'and open ends,providing said walls at both ends of each cell and adjacent the cornersthereof with slots, providing a flat rectangular frame of less overallthickness than said core, fitting said core into said frame with each ofits side faces disposed outwardly of theadjacent side face of saidframe, bending the portions of said cell walls between said slots atright angles to the remaining portions of said walls to form flangeswhose outer faces are substantially flush with adjacent side faces ofsaid frame, applying adhesive to said outer faces of said flanges, andsecuring a cover sheet to each 40, over the grid as it rests on aflat'surface, whereupon 7 the grid is turned over and the gang ofcutters is passed over the now upper surface forming the grid.

It will be understood that the grid composed of cells such as thoseshown in Figures 6 and 7 will be compressed by rollers of the same typeas that shown in Figure 3, so as 7 various alterations and modificationsmay be made such 4 side of said frame and said flanges.

2. A door construction comprising a flat rectangular frame, a flatcellular core fitted into said frame, the cells of said core beingpolygonal in cross section and open at their ends, said cells extendingtransversely of said core, each cell having. Walls, each Wall having atleast two slots, the part of each wall between the slots comprising aright angled flange arranged in parallel relation to the plane of thecore, the flanges at each end of each cell being separate from eachother, and a cover plate secured to eachside face of said frame and saidcore including, said flanges, said'core being compressed substantiallyequally on both sides and having a resiliency tending to force its sidefaces outwardly into engagement attaching said flanges to the coverplate located adjacent thereto.

References Cited in the file of this patent UNITED STATES PATENTS2,511,620 Clements June 13, 1950 2,537,026 Brugger Jan. 9, 1951 FOREIGNPATENTS 7 56,227 Sweden Mar. 11, 1924 60,158 France Mar. 24, 1954(Addition to No. 988,034.)

